1. Field of Invention
The present invention relates to an adapter and related signal transmission cables for converting a mobile telephone into a hands-free telephone system using an automobile sound system.
2. Description of Related Art
In recent years, numerous car accidents have been caused by drivers operating a hand-held telephone while driving. To solve this problem, many new hands-free telephone systems have been developed for car use. These developments are represented by Japanese patents No. 6-252821, No. 7-143051, No. 8-46678, No. 8-125727, No. 8-242275 and No. 9-84131, for example. In all these developments, equipment existing in a car is generally used. For example, car audio and loudspeaker system is used to audibilize received telephone signals.
In general, two methods are commonly used to achieve the required effects. In a first method, which is also described in Japanese Patent No. 8-46678, the car audio system, the mobile telephone and a car adapter are connected together to form a cable system. In a second method, which is disclosed in Japanese Patent No. 9-84131, a microphone is used for receiving the voice of a person in the car and then, the voice signal is transmitted to the mobile telephone through a wireless connection. The system also includes a wireless hands-free module, which is capable of receiving messages from the mobile phone and emitting signals. When the hands-free module receives a voice signal from the mobile phone, the signal will be sent to the loudspeakers of the car audio system.
However, to achieve the hands-free telephone system of the above two methods, sophisticated car adapter equipment must be installed. Therefore, the cost of installation is increased. Moreover, space must be made available in the car interior to house the additional module.
In light of the foregoing, there is a need in the art for a better hands-free car telephone system.